Identometer for transformer steels



Feb. 9, V1960 D, H, REIGHTER 2,924,772

IDENTOMETER FOR TRANSFORMER STEELS Filed Aug. 23, 1957 IN VENTOR.

IDENTOMETER FOR TRANSFORMER STEELS David H. Reighter, Roslyn, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Application August 23, 1957, serial No. 679,919 s claims. (c1. 324-34) This application relates to an apparatus and process for identifying various grades of grain oriented transformer steels and more particularly to an apparatus and process which will enable the aforesaid function to be accomplished with a speed and. facility applicable to receiving and production inspection.

Grain-oriented steels are an appreciable improvement over steels ordinarily used in making transformer cores and are characterized by high permeability at high inductions and low hysteresis loss. Armco, Hipersil and Corisil are well known trade names of grain-oriented steels.

Heretofore, the most widely used method, `and the method adopted by the American Society for Testing Materials for identifying grain-oriented transformer steels was the Epstein Core Loss Test. This test requires the operator to adjust many controls and read many meters as well as perform calculations thereafter in order to determine the grade of steel being tested.

In addition, the test specimen required for the Epstein test was very difficult to prepare. That is, the specimen comprised four elongated bundles arranged in a rectangle. Two of the bundles were made of strips cut in the direction of rolling and the other two bundles were made of strips cut at right angles to the direction of rolling. The bundles formed butt joints at the corners with tough paper of a critical thickness being interposed between adjacent bundles. It was also necessary to reduce magnetization to a minimum, by tapping the joints together, and thereafter clamping the corners to secure rigid joints.

The instant invention comprises a novel apparatus which will enable the operator to identify the grade of grain-oriented steels by referring to a single indicating means which is preferably the screen of an oscilloscope of the type commonly used in a laboratory or TVrepair shop. The pattern appearing on the scope due to the test specimen need merely be compared to the patterns obtained by using specimens having known grain orientation. All calculations are eliminated.

In addition to rapidly obtaining the desired information, the apparatus of this invention requires a test specimen which is especially simple to prepare. That is, the test specimen is a single piece having a disk shape with a central opening cut therethrough. A nine inch diameter disk has been found convenient.

With my apparatus the disk shaped test specimen is positioned so as to be part of the magnetic circuit between the poles of a permanent magnet. The specimen is rotated at a synchronous speed and at right angles to the lines of force of the magnet. Since the specimen comprises a grain-oriented steel the reluctance of the magnetic circuit will vary as the specimen is rotated in accordance with the relative orientation between the grains of the specimen and the lines of force. The varying re- I luctance will cause a corresponding variation `in the magnetic circuit flux.

.ited States Patent@ r"icc A core, having a pickup coil wound thereon, projects from either or both of the magnet poles and also forms part of the magnetic circuit. The changing llux WilI induce a signal in the pickup coil or coils. This signal is read as an induced voltage by connecting the pickup coil or coils in series across the vertical deflection terminals of an oscilloscope. The magnitude and/or shape of the signal generated by the test specimen is then compared to the signals generated in the pickup coil or coils by specimens of known grades.

If the test specimen is of a poor grade, that is, most of its grain orientation is random, the reluctance of the magnetic path will vary little as the specimen is rotated. Hence, the circuit ux will change very little and the signal induced in the pickup coil will be Very low since it is dependent on an inductive effect which is a function of the flux rate of change.

Conversely, if the test specimen is of a high grade,

when its grains are aligned in the direction of the lines of force the reluctance of the magnetic circuit will be very low and when the grains are aligned in the opposite direction the reluctance will be very high. Thus, the variation in reluctance, between very high and very low, will cause a rapid rate of change in the circuit fluxl thereby inducing a large signal in the pickup coil.

Accordingly, a primary object of the instant invention is to provide an apparatus and process for identifying `various grades of grain-oriented transformer steel with speed and accuracy.

Another object is to provide an identification apparatus and process requiring the reading of a single indicating device and in which the need for calculations is eliminated.

Still another object is to provide an identification apparatus and process requiring an easily constructed disk shaped specimen of the steel to be identiiied.

A further object is to provide an apparatus for rotating a specimen at synchronous speed through the lines of force of a magnet to induce a voltage in a pickup coil which is connected to the vertical deflection plates of an oscilloscope and comparing the scope presentation to that produced by specimens of known grades.

A still further object is to provide an apparatus Wherein the specimen being tested merely rests on a support rather than being clamped in any manner which might distort the true grain orientation.

These as well as other objects of the instant invention will become more apparent after reading the following description of the accompanying drawings in which:

Figure 1 is a side elevation of the apparatus of the instant invention.

Figure 2 is a typical oscillograph presentation when the test specimen comprises Armco 6x grain-oriented steel.

Figure 3 is a typical oscillograph presentation when the test specimen comprises Armco 7x grain oriented steel.

Figure 4 is a typical oscillograph presentation when the test specimen comprises Armco 8x grain-oriented steel.

Referring to the figures, sample or specimen 1-0 is a disk shaped member having a central opening through which non-metallic rod 12 passes. Rod 12 is an extension of output shaft 13 of synchronous motor 14 which provides constant speed rotation for non-metallic support disk 15.

Fastening means 11 removably secures support disc 15 to the end of rod 12. Sample 10 merely rests upon support 15,. No clamps, which could subject sample 1t) to steel.

distorting pressures and thereby upset the degree of orienfrom the periphery of support 15 -withrod ,12 vb eing posi- CII tioned .at the "midpoint of the line joining the poles 18,

19 so that support 15V runs ltrue to magnet 20.

Cores 21, having pickup coils 22 wound thereon, extend upward from pole faces A1,8, 19 close to the underside of support disk 15. Pickup coils 22, are connected in series aiding relationship withthe series combination being connected across .the vertical deflection terminals 2,3, 24 of oscilloscope 25 so that vpresentation 26 will appear on the .faceof the cathode ray tube2'7. Gridlines 23 are marked across the face for ready calibration and reading.

With the components oriented' as described, specimen and cores 21 comprise a major portion of the magnetic circuit between magnet poles ,16, 19. Any change .in reluctance ofthe circuit will `result'in an inverse change in the number of flux lines or magnetic lines ofjforce in the circuit. Since the flux lines alsoflink the turns of vpickup coils 22 any change in iiux will result in a signal being induced intheA pickup coils 22.

When support is rotated this brings about a corresponding rotation of yspecimen 10. As specimen 10 is rotated the grain orientation thereof will in varying degrees, depending ,upon the v.angular position, be in the lsame direction or in a direction opposite to the direction of the lines 'of force generated by magnet 20. The

:greater the degree of grain orientation in the specimen the higher the grade of steel and the lower will be the reluctance of the `magnetic circuit at the angular position where thespecimen grain orientation is in the same direction as theflux lines. Conversely, there is an angular 'position where the specimen grain orientation is opposite yangular speed the greatestrate of change of tlux-will -take place when the specimen is of the highest grade of grain oriented steel whilethe slowestrate of change of -tiux occurs when y'thespecimen is`ofthe lowest grade.

The flux rate of change induces signals in pickup coils 22 which signals are yviewedon oscilloscope 25. For most purposes it is sufficient to read the-signals merely las av voltagegenerated -by f Calibrating oscilloscope 25 with grid lines 28 facilitating the reading of thel voltages.

The greater the `deection the higher the degree of orientation and the lower the core loss.

It is necessary to establish thepelfect ofa generated voltage signal on each oscilloscope 25 by utilizing selected standardsamples. In-some lcases pictures of the .scope pattern may provemore exacting than an, attempt to count'thel grid spaces.

yIn this connection 1lFigures 2-4 illustrate'the scope traces obtained by using specimens of Armco transformer Armco'grades 6x, 7x, 8x cause the generation lof voltages having maximum spreads in the proportions of l3:ll:9 respectively, with 6X being the best grade of the three. Anexperienced operator wouldV soon recog- 31-31-of the type l8x trace and the dipsgZ preceding vthe peaks 33 of the type 7x trace.

lt is to be noted that my invention will operate satis- 'factorily' with only one coreZi and pickup coilj22 instead of the two illustrated in Figure 1.

In the foregoing, I have described my invention only in connection with preferred embodiments thereof. Many variations and modifications of the principles of my invention within the scope of the description herein are obvious. Accordingly, I prefer to be bound not by the specific disclosure herein but only by the appending claims.

I claim:

1.1An apparatus for identifying the grade of a disk shaped sample of grain-oriented steel; said apparatus comprising a permanent magnet having a pair of pole faces both located in thesame plane; a platform of nonmagnetic ,material operatively positioned for supporting said sample in a position such that said sample forms part plof -the .mgnetic circuit vbetween said pole faces; a synchronous motor having an output shaft whose axis is perpendicularto-s'aid plane and midway between said pole faces; said platform being secured to said shaft for rotation by said motor; a first core projecting from one of ksaid,pole faces; a first pickup coil lwound aboutsaid r'st core; said rst pickup coil having a pairof terminals adapted to be connected to the terminals of a visual indicating means.

2. An apparatus Ifor .identifying the grade of a disk shaped sample of grain-oriented steel; said apparatus comprisinga permanent magnet `hai/in gda pair vo f pole faces bothlocated in the same plane; a platformof nonlmagnetic material operativeiypositioned for supporting saidsample ina position such that said sample forms .partof the magnetic circuit between s aid pole faces; a

synchronous motor having an output shaft'whose axis is perpendicular to said plane and midway between said pole faces; said platform being secured to said shaft for rotation by said motor; a `first core projecting from one of said pole faces; a iirst pickup coil f woundabout said rst core; asecond core projecting from the other of said pole faces; a second pickup coil wound about said second core; said rst and second pickup coils being connected inelectrical series with the series connection being adapted for connection to the vertical Adeliection terminals of an oscilloscope.

3. An apparatus for identifying the grade of a sample -of ygrain-'oriented steel; said apparatus comprising a permanent magnet, a support platform, apickup device, a first means, a second means; said support platform Vbeing a Adisk shaped member comprisingla non-magnetic material; said magnetbeing a -U-shaped member; said support platform-being operatively positioned tosupport said sample so that it forms part of the magnetic 'circuit between the poles of said magnet; said -rst means rotating said support platform true to said magnet ata constant speed; said second means comprising-a core extending yfrom atleast one ofl the poles toward saidis'upport plat- `'form to a point adjacent` thereto; a coil associated with said core.

4. An apparatusfor identifying the grade of a sample of grain-oriented steel; said apparatus comprising a permanent magnet, a support platform, a pickup device, a

rst means, ya second means; said support platform being a disk shaped member comprising` a non-magnetic material; said magnet being a- U-shaped member; said support platform being operatively positioned to support said ofgrain-oriented steel; said apparatus comprising a permanent magnet; a pickup device, a iirst means and a second means; said magnet being a U-sh'aped member;

a support means for supporting said sample in a position to form a part of the magnetic circuit between the poles of said magnet; said rst means being operatively connected to said support means for rotating said sample 5 true to said magnet at a constant speed; said second means comprising a magnetic core extendingffrom at least one of the poles of said magnet toward said sample to a point adjacent to said sample; said pickup device comprising a coil wound on said core; said coil being electrically con- 10 nectible to the terminals of a visual indicating means.

References Cited in the le of this patent UNITED STATES PATENTS 

